This research program will continue to be concerned with the establishment of the primary structure of human hemoglobin variants, and studies of the functional properties induced by the amino acid substitution. The functional properties will emphasize the oxygenation function of hemoglobin as well as its solubility. Interactions of sickle cell hemoglobin with variant hemoglobins will be studied. The reactions of hemoglobins and chemically modified hemoglobins will be studied in an effort to elucidate the role of specific amino acid residues in the oxygenation function and solubility of liganded and unliganded hemoglobin. Other hemoglobin studies will be concerned with studies of the primary structure of rat hemoglobin, and with further studies on Belgrade rats which have a hereditary hypochromic anemia resembling thalassemia, and may ultimately serve as an animal model for thalassemia.